Middle of line (MOL) processes are one key determinant of device yield. The MOL processes include, for example, cobalt metallization and source/drain contact formation.
The cobalt metallization and source/drain contact formation processes, though, pose several challenges as technologies scale downwards. For example, cobalt metallization poses a significant challenge due to difficulties in controlling polishing processes, e.g., chemical mechanical polishing (CMP). Specifically, CMP processes for cobalt material are not highly selective, which results in poor process control. This poor process control, in turn, causes local thinning (e.g., lack of uniformity) of a sacrificial cap material that protects the gate material. The poor process control can also result in punch through of the sacrificial capping material, landing on the gate material. This will expose the gate material resulting in a shorting to subsequently formed source/drain contacts.